A polymerizable liquid crystal composition is useful as a component of an optically anisotropic medium, which is used, for example, as a phase difference film in various liquid crystal displays. A polymerizable liquid crystal composition is coated on a substrate, and is cured by irradiating it with radiation under the aligned condition due to an alignment layer, etc, to thereby obtain a phase difference film. However, in the case where a polymerizable liquid crystal composition is coated on a substrate, a tilt angle to an air interface occurs to an extent. Therefore, it is desired to reduce a tilt angle in order to satisfy optical properties required for a specific phase difference film.
As a method of reducing the aforementioned tilt angle, a method of adding a surfactant or a polymerizable surfactant in a polymerizable liquid crystal composition has been proposed (see Patent Reference 1, 2, and 3). Meanwhile, a method of incorporating a phase difference film in a liquid crystal cell of a liquid crystal display has attracted attention for the purpose of reduction in thickness, weight, and cost. In this case, there is a problem that impurities in the film are likely to have an adverse effect on a liquid crystal.
In the case where a surfactant is contained in a polymerizable liquid crystal composition, it is possible to achieve the purpose of reducing a tilt angle. However, in the case where a phase difference film is incorporated in a liquid crystal cell, because a surfactant chemical-structurally has a highly polar portion, a voltage-holding ratio of a liquid crystal deteriorates due to the contamination of a surfactant. In addition, a laminated film is difficult to form due to nonadhesive property and water and oil repellent properties which a surfactant possesses. In addition, in the case where a long-chain perfluoroalkyl sulfonamide derivative is used as a surfactant (see Patent Reference 3), because this compound has concerns for environmental toxicity, there is a problem for the use in a liquid crystal display.
As described above, a polymerizable liquid crystal composition has been desired, which has properties including no deterioration of a voltage-holding ratio of a liquid crystal display and easiness of forming a laminated film, and an effect of reducing a tilt angle to an air interface in the case where an optically anisotropic medium is prepared.
[Patent Reference 1]
Japanese Unexamined Patent Application, First Publication No. 2000-105315
[Patent Reference 2]
Japanese Unexamined Patent Application, First Publication No. 2003-105030
[Patent Reference 3]
Japanese Unexamined Patent Application, First Publication No. 2000-98133